Disturbances in the delivery of power to end user equipment are presently quite common. These disturbances may be brownout disturbances in which low power levels are delivered, or complete blackout situations in which no power is delivered. These disturbances occur for a variety of reasons but are frequently related to high demand situations (i.e., hot summer days when air conditioners and other end user equipment are run at peak levels) or delivery system equipment maintenance or failure.
Such disturbances that result in brownout or blackout situations can cause damage to end user equipment when voltage levels delivered to the equipment fall below required levels. This damage can cost end users a significant amount of money to either repair or replace the damaged equipment. Additionally, brownout or blackout situations cost utilities money and their own delivery system equipment may be damaged, requiring repair or replacement. Further, an isolated disturbance can affect a large number of end users if an entire subsystem load must be shed in response to the disturbance.
Some disturbances result in under voltage or under frequency events. An under voltage event occurs when a voltage level drops below a minimum or rated value. For example, electric consumer devices are frequently rated at 120 volts. While such devices may continue to operate uninterruptedly at values slightly below the rated voltage, the devices may be damaged or destroyed if the voltage delivered drops significantly, for example to 90 volts. Similarly, an under frequency event occurs when the frequency of a signal drops below a minimum or rated value. If an electronic device operates at a 60 Hertz signal, damage or destruction of the device may occur if the frequency drops to, for example, 40 Hertz. Some examples of systems that detect undervoltage and underfrequency conditions are disclosed and described in U.S. Pat. No. 3,993,984 to Penrod issued on Nov. 23, 1976, which is herein incorporated by reference. Consumers currently have no adequate way of protecting their equipment during under voltage or under frequency events.
Presently, systems exist in which utilities monitor and control end user equipment remotely to control load levels. These systems, however, are controlled by the utility and are primarily only used in peak demand situations. These systems typically do not operate to protect end user equipment in non-peak demand situations. Further, present systems may not provide a sufficiently rapid response to decreasing power delivery levels to protect end user equipment from damage; it may take a utility control center operator several minutes or more to respond to a system disturbance. Additionally, present systems may not operate to automatically shed load in under voltage or under frequency conditions to aid a utility in bringing the voltage or frequency back up to standard. One prior art system proposes to initiate load shedding via demand load control of air conditioning compressors and the like by lowering the frequency output at the utility thereby tripping frequency-sensitive switches located close to the load. For further details on such a system, reference is made to U.S. Pat. No. 5,687,139 to Budney issued Nov. 11, 1997, which is incorporated herein by reference.
There is a need in the industry for an apparatus or device that protects a consumer's end user equipment from electric distribution power delivery disturbances, primarily under frequency events, is located internally in end user equipment, and is automatic in its response, thereby substantially reducing the need for utilities to directly monitor end user equipment in instances of frequency drop offs.